(1) Field of the Invention
The present invention relates to a machine for cleaning ballast along the shoulders of a railroad track mounted on the track for mobility in an operating direction, the track consisting of two rails fastened to ties having transversely opposite ends at the track shoulders, which comprises a machine frame having transversely opposite sides adjacent the track shoulders, a respective endless ballast excavating and conveying chain vertically adjustably mounted at a respective one of the machine frame sides, a ballast screening installation arranged to receive the excavated ballast conveyed by the endless chains, and a respective ballast loosening and excavating device vertically adjustably mounted on the machine frame, each device including a ballast loosening and excavating tool arranged to project below a respective one of the tie ends in a vertically adjusted operating position and ballast guide plate means arranged adjacent the tool.
(2) Description of the Prior Art
Mobile ballast cleaning machines of this type have been used on tracks over which coal is transported. The ballast in the shoulders of such tracks becomes very dirty because of the accumulation of coal dust settling thereon as such coal dust trickles from the passing freight cars in which the coal is transported. This encrustation of the ballast bed causes drainage problems. In the known mobile ballast cleaning machines, the dirty shoulder ballast is excavated by the endless chains at the sides of the machine frame and conveyed to a trailing ballast screening installation where it is cleaned. The ballast loosening and excavating device trails the endless ballast excavating and conveying chain in the operating direction and serves to scrape and remove the dirty ballast in the range of the tie end, which has not been excavated by the chain which is transversely spaced from the tie end. This ballast is guided by a guide plate transversely outwardly from the tie end into the area of the track shoulder previously excavated by the chain and partially fills this excavated track shoulder area. A ballast distributing chute follows the ballast loosening and excavating device in the operating direction to discharge the cleaned ballast in this partially filled track shoulder area. This has the disadvantage that the dirty ballast loosened and excavated from under the tie ends is mixed with the cleaned ballast so that the ballast shoulders still contain coal dust-contaminated ballast.
U.S. Pat. No. 4,635,664, dated Jan. 13, 1987, discloses a mobile machine for cleaning ballast along the shoulders of a railroad track, wherein the dirty ballast excavated along the shoulders is conveyed to a washing installation and the washed ballast is then conveyed to a ballast screening installation. This washed and screened ballast is then redistributed in the excavated shoulder areas and smoothed by means of a ballast plow. However, this machine is not well adapted for use with coal dust-contaminated ballast because the coal dust is merely smeared over the ballast in the washing installation and cannot be removed therefrom in the succeeding screening installation.